A major ongoing focus of SPARC is on quantifying the evolution of stratospheric ozone and its interaction with climate change. Through its Initiative on Halogen Chemistry it will clarify recent laboratory results concerning the role of key interactions in ozone depletion and provide direct input to the 2010 WMO/UNEP Ozone Assessment.

The SPARC CCMVal activity continues to improve understanding of the performance of Chemistry-Climate
Models and their underlying general circulation models through process-oriented evaluation, along with coordinated analysis of science results. Key diagnostics with respect to radiation, dynamics, transport, and stratospheric chemistry and microphysics, following from atmospheric constituent distributions, are used to compare model outputs with robust relationships found in observations. The AC&C initiative couples this effort with model studies of the impacts of climate on atmospheric chemistry, the impact of atmospheric chemistry on climate, and the impact of climate on air quality.

AC&C will help the scientific community to identify a set of high priority science questions around atmospheric chemistry and climate that require integration and synthesis across the projects. Through a set of common diagnostics that can be used to address the uncertainties, the modelling and measurement communities will cooperate to constrain the models and use them to inform measurement planning. AC&C will also evaluate emissions inventories and undertake an effort to harmonize them and create a platform for their coordinated development in the future.

The tropopause region (including both the tropical and extra-tropical tropopause layers) is the location of major exchanges of radiatively and chemically active species (e.g. water vapour, methane, ozone depleting substances, ozone itself, and other radiatively important species) between the troposphere and stratosphere. Understanding the physical and dynamical processes governing and constraining this region, for instance processes determining the location and magnitude of the cold-point temperature, is critical to evaluating and modelling climate sensitivity as well as for modelling of very short-lived species . These issues will be addressed through the SPARC Tropopause Initiative and SPARC-GEWEX-IGAC collaborative activities on modelling the role of deep convection in stratosphere- troposphere coupling and exchange, particularly in the region of the tropical tropopause